Method for manufacturing porous honeycomb structure and honeycomb body

ABSTRACT

A method of manufacturing a porous honeycomb structure of the present invention includes the steps of: mixing and kneading at least an aggregate particle material formed of a ceramic and/or a metal, water, an organic binder, a pore former, and colloidal particles to form clay; forming the clay into a honeycomb shape having a plurality of cells constituting through channels of fluids; drying the clay to obtain a honeycomb formed body; calcining the honeycomb formed body to form a calcined body; and thereafter firing the calcined body to obtain the porous honeycomb structure.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a poroushoneycomb structure preferably for use as a filter for collecting soot,and a honeycomb formed body, particularly to a method of manufacturing aporous honeycomb structure, capable of effectively preventing asituation in which the porous honeycomb structure is cracked orcollapsed because of its own weight in manufacturing the poroushoneycomb structure having a high porosity, and a honeycomb formed body.

BACKGROUND ART

A porous honeycomb structure formed of a ceramic superior in resistanceto heat or corrosion has been used as a filter for collecting soot, foruse in applications such as environmental measures for preventingpollution and the like and product recovery from a high-temperature gasin various fields including chemistry, electric power, iron and steel,and industrial waste disposal. For example, the porous honeycombstructure formed of a ceramic has been preferably used as a filter forcollecting the soot, for use in a high-temperature corrosive gasatmosphere, such as a diesel particulate filter (DPF) which collectsparticulates discharged from a diesel engine.

Examples of the soot collecting filter using the porous honeycombstructure include a structure in which, for example, as shown in FIG. 1,an inlet-side end face B and an outlet-side end face C of a plurality ofcells 23 of a porous honeycomb structure 21 are alternately plugged byplugging portions 22. According to the porous honeycomb structurestructured in this manner, when a gas G₁ to be treated is introducedinto cell 23 from the inlet-side end face B, the particulates arecaptured by partition walls 24. On the other hand, a treated gas G₂which has flown into the adjacent cell 23 through the porous partitionwall 24 is discharged from the outlet-side end face C. Therefore, thetreated gas G₂ from which the particulates in the gas G₁ to be treatedhave been separated can be obtained.

Especially, in recent years, since a treatment capability of the sootcollecting filter needs to be enhanced, there has been a demand for ahigh-porosity porous honeycomb structure having a small pressure lossamong the above-described porous honeycomb structures. As a method ofmanufacturing such high-porosity porous honeycomb structure, a method ofmanufacturing a porous honeycomb filter has been described in which acordierite material, water, additionally a binder (organic binder suchas methyl cellulose, a pore former (organic material such as graphite)and the like are kneaded, and a plasticized plastic material (equivalentto “clay” mentioned in the present description) is formed, dried, andfired (see, e.g., Japanese Patent Application Laid-Open No.2002-219319). According to the manufacturing method, since the binder orthe pore former is burnt down to thereby form pores in firing a formedbody, the high-porosity porous honeycomb structure can be obtained.

However, in the above-described manufacturing method, when a largeamount of binder and pore former are contained in the clay for a purposeof manufacturing a higher-porosity porous honeycomb structure, theporous honeycomb structure is cracked during the firing of the formedbody, and in an extreme case, there has been a problem that the poroushoneycomb structure collapses by its own weight.

DISCLOSURE OF THE INVENTION

The present invention has been developed in consideration of theabove-described problems of the conventional techniques, and an objectthereof is to provide a method of manufacturing a porous honeycombstructure, capable of effectively preventing a situation in which theporous honeycomb structure is cracked or collapsed by its own weight infiring a formed body, and a honeycomb formed body.

As a result of intensive studies to solve the above-described problems,the present inventor has found that the above-described object can beachieved, when colloidal particles are contained in clay for use in theforming, and has completed the present invention. That is, according tothe present invention, there are provided the following method ofmanufacturing a porous honeycomb structure, and honeycomb formed body.

[1] A method of manufacturing a porous honeycomb structure, comprisingthe steps of: mixing and kneading at least an aggregate particlematerial formed of a ceramic and/or a metal, water, an organic binder, apore former, and colloidal particles to thereby form clay; forming theclay into a honeycomb shape having a plurality of cells constitutingthrough channels of fluids; drying the clay to thereby obtain ahoneycomb formed body; calcining the honeycomb formed body to therebyobtain a calcined body; and thereafter firing the calcined body tothereby obtain the porous honeycomb structure.

[2] The method of manufacturing the porous honeycomb structure accordingto the above item [1], wherein the clay contains 0.1 to 10 parts by massof the colloidal particles with respect to 100 parts by mass of theaggregate particle material.

[3] The method of manufacturing the porous honeycomb structure accordingto the above item [1] or [2], wherein the clay contains an alkali metalsource corresponding to 0.01 to 10 parts by mass of an alkali metal interms of the alkali metal with respect to 100 parts by mass of theaggregate particle material.

[4] The method of manufacturing the porous honeycomb structure accordingto any one of the above item [1] to [3], wherein the aggregate particlematerial contains at least one type of component selected from a groupconsisting of a cordierite material, mullite, alumina, aluminumtitanate, lithium aluminum silicate, silicon carbide, silicon nitride,and metal silicon, and a total of the mass of the component occupies 50%by mass or more with respect to a total mass of the aggregate particlematerial.

[5] A honeycomb formed body comprising: clay containing at least anaggregate particle material formed of a ceramic and/or a metal, water,an organic binder, a pore former, and colloidal particles, the claybeing formed into a honeycomb shape having a plurality of cellsconstituting through channels of fluids.

[6] The honeycomb formed body according to the above item [5], whereinthe clay contains 0.1 to 10 parts by mass of the colloidal particleswith respect to 100 parts by mass of the aggregate particle material.

[7] The honeycomb formed body according to the above item [5] or [6],wherein the clay contains an alkali metal source corresponding to 0.01to 10 parts by mass of an alkali metal in terms of the alkali metal withrespect to 100 parts by mass of the aggregate particle material.

[8] The honeycomb formed body according to any one of the above items[5] to [7], wherein the aggregate particle material contains at leastone type of component selected from a group consisting of a cordieritematerial, mullite, alumina, aluminum titanate, lithium aluminumsilicate, silicon carbide, silicon nitride, and metal silicon, and atotal of the mass of the component occupies 50% by mass or more withrespect to a total mass of the aggregate particle material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of a filter forcollecting soot, using a porous honeycomb structure;

FIG. 2 is a schematic diagram showing a “honeycomb shape” by an exampleof the porous honeycomb structure; and

FIG. 3 is a schematic diagram showing a method of evaluating strength ofa calcined body.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode for carrying out a method of manufacturing a poroushoneycomb structure of the present invention will be describedconcretely hereinafter.

To develop the method of manufacturing the porous honeycomb structure ofthe present invention, the present inventor has first studied reasonswhy the porous honeycomb structure is cracked or collapsed by its wonweight in firing a formed body. As a result, it has been considered as afirst reason that when the formed body is fired, a large amount ofbinder and pore former burn and generate heat, accordingly temperatureof the formed body being fired rapidly rises, and a large thermal stressis generated. As a second reason, the binder contained in the clay isgelled, and functions as a reinforcing agent to maintain a mechanicalstrength of the formed body in the formed body before fired. However,during the firing of the formed body, the binder which has functioned asthe reinforcing agent is burnt down, and a phenomenon occurs in whichthe mechanical strength of the formed body being fired rapidly drops.Moreover, as a third reason, this phenomenon becomes more remarkable ina high-porosity structure after the pore former burns down.

To solve the problem, in the present invention, a material whichfunctions as the reinforcing agent even after the binder burns down isseparately added to the clay for use in the forming. Concretely, theclay for use in the forming contains colloidal particles such as silicasol. Since the colloidal particles harden by dehydration condensationreaction or the like at a comparatively low temperature, the particlesfunction as the reinforcing agent even after the binder burns down, andthe drop of the mechanical strength of the formed body (furthermore theporous honeycomb structure) can be prevented. Therefore, a situation inwhich the porous honeycomb structure is cracked can be effectivelyprevented even in a case where a large amount of binder and pore formerburn and generate heat, accordingly the temperature of the formed bodybeing fired rapidly rises, and a large thermal stress is generated. Asituation in which the porous honeycomb structure collapses by its ownweight can be effectively prevented even in the high-porosity structureafter the pore former has burnt down.

{circle around (1)} First Step (Preparation of Clay)

In the manufacturing method of the present invention, first, at least anaggregate particle material formed of a ceramic and/or a metal, water,an organic binder, a pore former, and colloidal particles are mixed andkneaded to thereby form clay.

Aggregate particles are particles which constitute main constitutingcomponents of a porous honeycomb structure (sintered body), and theaggregate particle material is a raw material substance. The aggregateparticle material in the present invention contains at least one type ofcomponent selected from a group consisting of a cordierite material,mullite, alumina, aluminum titanate, lithium aluminum silicate, siliconcarbide, silicon nitride, and metal silicon, and a total of the mass ofthe component occupies 50% by mass or more with respect to a total massof the aggregate particle material. This is preferable from a viewpointof enhancing resistance to heat.

The “cordierite material” mentioned in the present description means asubstance converted into cordierite by the firing, and, for example,talc, kaolin, alumina, silica and the like are mixed in such a mannerthat a fired composition is a theoretical composition(2MgO.2Al₂O₃.5SiO₂) of cordierite. Metal silicon is not a ceramic, butis sometimes a constituting material of an Si—SiC sintered body in whichsilicon carbide and metal silicon are the aggregate particle materials.

The organic binder is an additive which is gelled in the formed body(clay) before fired and which performs a function of a reinforcing agentto maintain the mechanical strength of the formed body. Therefore, asthe binder, organic polymers capable of being gelled in the formed body(clay) are preferably usable such as hydroxypropoxyl methyl cellulose,hydroxypropyl methyl cellulose, methyl cellulose, hydroxyethylcellulose, carboxyl methyl cellulose, and polyvinyl alcohol.

The pore former is an additive which burns down during the firing of theformed body and which forms pores to thereby increase porosity, so thata high-porosity porous honeycomb structure is obtained. Therefore,examples of the pore former include organic materials which burn downduring the firing of the formed body, such as graphite, flour, starch,phenol resin, polymethyl methacrylate, polyethylene, and polyethyleneterephthalate. Above all, a microcapsule (acrylic resin-basedmicrocapsule, etc.) formed of a foam resin is especially preferablyusable. Since the microcapsule formed of the foam resin is hollow, ahigh-porosity porous honeycomb structure can be obtained by a smallamount of added microcapsule. Additionally, there is an advantage thatlittle heat is generated at a firing time, and generation of thermalstress can be reduced.

The colloidal particles are additives which harden by dehydrationcondensation reaction or the like at a comparatively low temperature andwhich function as the reinforcing agent to bind aggregate particles toone another even after the binder burns down. Examples of the colloidalparticles include colloidal particles formed of an inorganic materialwhich does not burn down during the firing of the formed body, such assilica sol, alumina sol, metal alcoxide, and water glass. The colloidalparticles whose hardening temperature is low as compared with burningtemperature of the binder or the pore former for use are preferablyselected from these colloidal particles and used. The added amount andcomposition of the colloidal particles to be added are preferablyselected, and used as a part of a starting material in such a manner asto be adapted to a target sintered body composition.

As a content of the colloidal particles, the clay for use in the formingpreferably contains 0.1 to 10 parts by mass of the colloidal particleswith respect to 100 parts by mass of the aggregate particle material,more preferably contains 0.2 to 5.0 parts by mass of colloidalparticles, and especially preferably contains 0.4 to 2.0 parts by massof colloidal particles.

When the content of the colloidal particles is set in theabove-described range, in calcining and firing steps, the obtainedcalcined body has a strength of at least 0.01 kg/cm² or more, and asituation in which the calcined body (furthermore the porous honeycombstructure) is cracked or collapsed by its own weight can be effectivelyprevented (it is to be noted that a method of measuring theabove-described strength will be described in detail in paragraphs ofexamples). On the other hand, when the content of the colloidalparticles is less than the above-described range, the content isunfavorable in that the effect of maintaining the mechanical strength ofthe calcined body is insufficient after the burn-down of the binder.When the content exceeds the above-described range, the content isunfavorable in that the effect of maintaining the mechanical strength ofthe calcined body is fulfilled, but the colloidal particles fill in thepores of the calcined body (furthermore the porous honeycomb structure),and the porosity drops.

The clay in the present invention needs to contain at least theaggregate particle material, water, organic binder, pore former, andcolloidal particles. When the aggregate particle material containssilicon (cordierite material, mullite, lithium aluminum silicate,silicon carbide, silicon nitride, metal silicon, etc.), an alkali metalsource is preferably contained. The alkali metal source forms hydroxidewhen dissolved in a water content in the clay, and reacts with silicaunavoidably present on the surface of the silicon-containing aggregateparticle material to form alkali silicate glass (water glass) (see thefollowing reaction formula (1)). This alkali silicate glass functions asthe reinforcing agent even after the binder burns down, and the drop ofthe mechanical strength of the formed body (furthermore the poroushoneycomb structure) can be prevented.2KOH+SiO₂→K₂O.SiO₂+H₂O   (1)

The alkali metal source is not especially limited as long as thematerial is capable of reacting with water to thereby discharge alkalimetal ions, and examples thereof include inorganic salts of alkalimetals, such as oxide and hydroxide, and organic salts of alkali metals,such as fatty acid salt. The type of the alkali metal is not especiallylimited, but potassium and sodium are preferable.

As the content of the above-described alkali metal source, the clay foruse in the forming preferably contains an alkali metal sourcecorresponding to 0.01 to 10 parts by mass of a alkali metal in terms ofthe alkali metal with respect to 100 parts by mass of the aggregateparticle material, more preferably contains the alkali metal sourcecorresponding to 0.02 to 5 parts by mass, and especially preferablycontains the alkali metal source corresponding to 0.03 to 1 part bymass.

The above-described clay may contain another additive if necessary. Forexample, a dispersant (surfactant) or the like for promoting dispersioninto water which is a dispersion medium may be contained. Examples ofthe dispersant include ethylene glycol, dextrin, fatty acid soap,polyalcohol and the like.

The above-described aggregate particle material, water, organic binder,pore former, colloidal particles and the like are mixed and kneaded, forexample, by a vacuum kneading machine to thereby prepare clay having anappropriate viscosity.

{circle around (2)} Second Step (Forming and Drying)

Next, the clay prepared as described above is formed into a honeycombshape having a plurality of cells constituting through channels offluids, and dried to thereby obtain a honeycomb formed body.

The “honeycomb shape” mentioned in the present description means ashape, for example, of a porous honeycomb structure 1 shown in FIG. 2,which is partitioned by remarkably thin partition walls 4 to therebyform a plurality of cells 3 constituting the through channels of thefluids. A whole shape of the honeycomb formed body is not especiallylimited, and examples of the shape include not only a cylindrical shapeshown in FIG. 2 but also a quadratic prism shape and a triangular prismshape. A cell shape (cell shape in a section vertical to a cell formingdirection) of the honeycomb formed body is not especially limited, andexamples include shapes of not only a quadrangular cell shown in FIG. 2but also a hexagonal cell and a triangular cell.

A forming method is not especially limited, known forming methods suchas extrusion forming, injection forming, and press forming haveheretofore been usable, and above all a method is preferably usable inwhich the clay prepared as described above is extruded using a diehaving a desired cell shape, partition wall thickness, and cell density.A drying method is not especially limited, known drying methods such ashot air drying, microwave drying, dielectric drying, reduced-pressuredrying, vacuum drying, and freezing drying have heretofore been usable,and above all a drying method obtained by combining the hot air dryingand the microwave drying or the dielectric drying is preferable in thatthe whole formed body can be quickly and uniformly dried.

The honeycomb formed body of the present invention obtained as describedabove comprises the clay containing at least the aggregate particlematerial formed of a ceramic and/or a metal, water, organic binder, poreformer, and colloidal particles, and the honeycomb formed body is formedinto the honeycomb shape having a plurality of cells constituting thethrough channels of fluids. The honeycomb formed body fulfills an effectof being capable of effectively preventing a situation in which theporous honeycomb structure is cracked or collapsed by its own weight infiring the formed body. Especially when the clay contains 0.1 to 10parts by mass of colloidal particles with respect to 100 parts by massof the aggregate particle material, the effect becomes greater.

{circle around (3)} Third Step (Calcining)

Furthermore, the honeycomb formed body obtained as described above iscalcined (degreased) to thereby form a calcined body. The calciningmeans an operation to burn and remove organic materials (binder, poreformer, dispersant, etc.) in the formed body, and the hardening by thedehydration condensation reaction or the like of the colloidal particlesis also simultaneously performed in the manufacturing method of thepresent invention. In general, since the burning temperature of thebinder is about 160° C., and that of the pore former is about 300° C., acalcining temperature may be set to about 200 to 1000° C. A calciningtime is not especially limited, but is usually about 1 to 10 hours.

{circle around (4)} Fourth Step (Firing)

Finally, the calcined body obtained as described above is fired tothereby obtain a porous honeycomb structure. The firing is an operationfor sintering and densifying the aggregate particle material in thecalcined body to secure a predetermined strength. Since firingconditions (temperature and time) differ with the type of the aggregateparticle material, appropriate conditions may be selected in accordancewith the type of the aggregate particle material for use. For example,when the cordierite material is used as the aggregate particle material,the body is preferably fired at a temperature of 1410 to 1440° C. for 3to 7 hours.

EXAMPLES

The present invention will be further concretely described in accordancewith examples in which high-porosity porous honeycomb structures havinga porosity of 60% were manufactured, and comparative examples.Additionally, there is not any limitation to the present invention bythese examples. It is to be noted that with regard to average particlediameters of aggregate particle materials in the following examples andcomparative examples, a value of 50% particle diameter was used whichwas measured by an X-ray transmission system grain size distributionmeasuring device (e.g., Sedigraph 5000-02 type manufactured by ShimadzuCorp.) using a Stokes' liquid-phase precipitation method as ameasurement principle and performing detection by an X-ray transmissionmethod.

[Manufacturing of Honeycomb Formed Body]

Example 1

As an aggregate particle material, a total of 100 parts by massincluding 80 parts by mass of silicon carbide powder having an averageparticle diameter of 33.0 μm, and 20 parts by mass of metal siliconpowder having an average particle diameter of 4.0 μm were prepared.Moreover, with respect to 100 parts by mass of this aggregate particlematerial, 1.2 parts by mass (in terms of solid content) of silica solwhich was colloidal particles, and 0.3 parts by mass of potassiumlaurate which was an alkali metal source were added. Furthermore, methylcellulose and hydroxypropyl methyl cellulose which were organic binders,starch which was a pore former, and an appropriate amount of water wereadded, and mixed and kneaded by a vacuum kneading machine to prepareclay.

The above-described clay was formed into a honeycomb shape by extrudingthe clay using a die having a cell shape, partition wall thickness, andcell density described later, and thereafter dried by a drying methodobtained by combining hot air drying and microwave drying to obtain ahoneycomb formed body. As to a whole shape of the obtained honeycombformed body, an end-face (cell opening surface) shape was a 35 mm×35 mmsquare, a length was 152 mm, a cell shape was an about 1.15 mm×1.15 mmsquare cell, the thickness of the partition wall was 310 μm, the celldensity was about 46.5 cells/cm² (300 cells/square inch), and a totalcell number was 576 cells.

Examples 2, 3

A honeycomb formed body was obtained in the same manner as in Example 1except that an added amount of colloidal particles was set to 0.1 partsby mass (Example 2), and 10.0 parts by mass (Example 3).

Example 4

As an aggregate particle material, a total of 100 parts by massincluding 98 parts by mass of alumina powder having an average particlediameter of 6.0 μm, and 2 parts by mass of silica powder having anaverage particle diameter of 5.0 μm were prepared. Moreover, withrespect to 100 parts by mass of this aggregate particle material, 1.5parts by mass (in terms of solid content) of alumina sol which wascolloidal particles were added. Furthermore, methyl cellulose andhydroxypropyl methyl cellulose which were organic binders, starch whichwas a pore former, ethylene glycol which was a dispersant (surfactant),and an appropriate amount of water were added, and mixed and kneaded bya vacuum kneading machine to prepare clay.

The above-described clay was formed into a honeycomb shape by extrudingthe clay using a die having a cell shape, partition wall thickness, andcell density described later, and thereafter dried by a drying methodobtained by combining hot air drying and dielectric drying to obtain ahoneycomb formed body. As to a whole shape of the obtained honeycombformed body, an end-face (cell opening surface) shape was a 50 mm×50 mmsquare, a length was 50 mm, a cell shape was an about 2.1 mm×2.1 mmsquare cell, the thickness of the partition wall was 440 μm, the celldensity was about 15.5 cells/cm² (100 cells/square inch), and a totalcell number was 400 cells.

Comparative Example 1

A honeycomb formed body was obtained in the same manner as in Example 1except that any colloidal particle or alkali metal source was not added.

Comparative Example 2

A honeycomb formed body was obtained in the same manner as in Example 1except that an added amount of colloidal particles was set to 15.0 partsby mass.

[Calcining]

The honeycomb formed bodies of Examples 1 to 4 and Comparative Examples1 and 2 described above were calcined (degreased) at about 400° C. inthe atmosphere for five hours to thereby obtain calcined bodies.

[Firing]

The calcined bodies of Examples 1 to 3 and Comparative Examples 1 and 2described above were fired at about 1450° C. in an argon atmosphere fortwo hours to thereby obtain porous honeycomb structures. The calcinedbody of Example 4 was fired at about 1650° C. in the atmosphere for twohours to thereby obtain a porous honeycomb structure.

[Evaluation]

With regard to the calcined bodies and the porous honeycomb structuresof Examples 1 to 4 and Comparative Examples 1 and 2 described above,{circle around (1)} strength of the calcined body, {circle around (2)}state of the calcined body, and {circle around (3)} porosity of theporous honeycomb structure were evaluated by the following method.

{circle around (1)} Strength of Calcined Body

The strength was measured in conformity to “Compressive Strength TestMethod of Fine Ceramics” described in JIS R 1608”. Concretely, first,cubic bodies of honeycomb structures of the respective examples andcomparative examples having the same cell shape, partition wallthickness, and cell density and having one side of 35 mm were extrudedusing the clays prepared in Examples 1 to 4 and Comparative Examples 1and 2, and were dried and calcined by the same drying and calciningmethods to prepare test pieces. Subsequently, as shown in FIG. 3, apressure was applied to a test piece 31 toward a forming direction ofcells 31 a by pressurizing plates 32, and compressive strengths weremeasured to thereby evaluate the strengths of the calcined bodies. It isto be noted that the compressive strength was calculated by assumingthat the cubic body of the honeycomb structure was a solid body, anddividing a maximum load by 35×35 (mm²). Results are shown in Table 1.

{circle around (2)} State of Calcined Body

Presence of generation of crack in the calcined body, and presence ofcollapse of the calcined body by its own weight were visually observedto thereby evaluate a state of the calcined body. Results are shown inTable 1.

{circle around (3)} Porosity of Porous Honeycomb Structure

A porosity of the porous honeycomb structure was measured by mercuryporosimetry to thereby evaluate the porosity of the porous honeycombstructure. Results are shown in Table 1. TABLE 1 Porosity ColloidalStrength of particle of porous Amount calcined State honey- Aggregate(parts body of comb particle by (kg/ calcined struc- material Type mass)cm²) body ture (%) Ex. 1 Silicon Silica 1.2 0.1 No 60 carbide/metal Solcrack● silicon (80:20) collapse Ex. 2 Silicon Silica 0.1 0.01 No 60carbide/metal Sol crack● silicon (80:20) collapse Ex. 3 Silicon Silica10 8 No 58 carbide/metal Sol crack● silicon (80:20) collapse Ex. 4Alumina/silica Alumina 1.5 0.5 No 60 (98:2) Sol crack● collapse C.E.1Silicon — — 0.005 Col- 60 carbide/metal lapse silicon (80:20) C.E.2Silicon Silica 15 20 No 40 carbide/metal Sol crack● silicon (80:20)collapse[Results]

The calcined bodies of Examples 1 to 4 had a strength of at least 0.01kg/cm² or more, and the strength was remarkably enhanced as comparedwith the calcined body of Comparative Example 1. The generation of thecrack or the collapse by the weight was not recognized in any of thecalcined bodies of Examples 1 to 4. Furthermore, the porous honeycombstructures of Examples 1 to 4 maintained the porosity equal to that ofthe porous honeycomb structure of Comparative Example 1, and any drop ofthe porosity was not recognized.

On the other hand, the calcined body of Comparative Example 1 had astrength of only 0.005 kg/cm², and the strength was remarkably low. Itwas not possible to prevent the collapse by the weight in the calcinedbody of Comparative Example 1.

Moreover, the calcined body of Comparative Example 2 had a strength of20.0 kg/cm², the strength was remarkably enhanced as compared with thecalcined body of Comparative Example 1, the generation of the crack orthe collapse of the weight was not recognized, but the porosity of theporous honeycomb structure of Comparative Example 2 largely dropped ascompared with the porous honeycomb structure of Comparative Example 1.That is, it was not possible to obtain the porous honeycomb structurehaving a targeted high porosity (porosity of 60%).

INDUSTRIAL APPLICABILITY

As described above, since colloidal particles are contained in clay foruse in the forming in a method of manufacturing a porous honeycombstructure of the present invention, it is possible to effectivelyprevent a situation in which the porous honeycomb structure is crackedor collapsed by its own weight during the firing of a formed body.

1.-8. (canceled)
 9. A method of manufacturing a porous honeycombstructure, characterized by: mixing and kneading at least an aggregateparticle material composed of a ceramic and/or a metal, water, anorganic binder, a pore former, and colloidal particles to form clay;forming the clay into a honeycomb shape having a plurality of cellsconstituting through channels of fluids; drying the clay to obtain ahoneycomb formed body; calcining the honeycomb formed body to form acalcined body; and thereafter firing the calcined body to obtain theporous honeycomb structure.
 10. The method of manufacturing the poroushoneycomb structure according to claim 9, wherein the clay contains 0.1to 10 parts by mass of the colloidal particles with respect to 100 partsby mass of the aggregate particle material.
 11. The method ofmanufacturing the porous honeycomb structure according to claim 9,wherein the clay contains an alkali metal source corresponding to 0.01to 10 parts by mass of an alkali metal in terms of the alkali metal withrespect to 100 parts by mass of the aggregate particle material.
 12. Themethod of manufacturing the porous honeycomb structure according toclaim 9, wherein the aggregate particle material contains at least onetype of component selected from a group consisting of a cordieritematerial, mullite, alumina, aluminum titanate, lithium aluminumsilicate, silicon carbide, silicon nitride, and metal silicon, and atotal of the mass of the component occupies 50% by mass or more withrespect to a total mass of the aggregate particle material.
 13. Ahoneycomb formed body characterized by comprising: clay containing atleast an aggregate particle material composed of a ceramic and/or ametal, water, an organic binder, a pore former, and colloidal particles,the clay being formed into a honeycomb shape having a plurality of cellsconstituting through channels of fluids.
 14. The honeycomb formed bodyaccording to claim 13, wherein the clay contains 0.1 to 10 parts by massof the colloidal particles with respect to 100 parts by mass of theaggregate particle material.
 15. The honeycomb formed body according toclaim 13, wherein the clay contains an alkali metal source correspondingto 0.01 to 10 parts by mass of an alkali metal in terms of the alkalimetal with respect to 100 parts by mass of the aggregate particlematerial.
 16. The honeycomb formed body according to claim 13, whereinthe aggregate particle material contains at least one type of componentselected from a group consisting of a cordierite material, mullite,alumina, aluminum titanate, lithium aluminum silicate, silicon carbide,silicon nitride, and metal silicon, and a total of the mass of thecomponent occupies 50% by mass or more with respect to a total mass ofthe aggregate particle material.